A good place to start is Emerging Church Information, a site which has been designed as a forum where stories are told and reflected upon and opportunity given for people to enter into debate on the issues surrounding new ways of being church.
Emergent Village is a US site. "Emergent is a growing generative friendship among missional Christian leaders." Emergent Village offers a good range of resources. 'Friends' are those who subscribe to a basic approach:
There is also a version of Emergent in the UK.
The web log (blog) has been a fertile source of speculation and conversation about emerging church. There is something about the transitory and transitional nature of the blog that seems apt.
Maggi Dawn is a Church of England priest and musician who has been interested in new ways of being church for some time.
Jonny Baker has been involved in alt.worship for many years, leading Grace at St Mary's, Ealing for a number of years.
Alternative Worship offers a portal site with links to many other alternative worship sites. It also has a lot of resources on how and why. (There is another alternative worship portal site here but it is nowhere near as good.)
Grace is the alternative worship congregation I know best, having started at St Mary's, Ealing ten years ago (I left St Mary's about five years ago).
Moot is also known to me because Ian Mobbs trained with the East Region Ministry Course, with whom I have shared a number of happy weekends during my own training as an Ordained Local Minster. They led worship for us in their style at a time when I was particularly sensitive to the possibility of transformation and had a profound effect on my own thinking.
Stephen Shields has an interesting perspective on postmodernism which tries to relate postmodern ideas to the emerging church agenda.
Thomas Hohstadt's FutureChurch site promotes his books, has some interesting articles and a message board. You can also sign up for his e-newsletter.
One approach to cell church is Carl George's Metachurch. (This now directs you to leadership for Ministry, which seems to be mainly an advert for his leadership course.)
The Alleon site has a lot of free articles under different headings: Community, Spirituality, Culture, Leadership, Mission, Resources, General & Columns. You have to sign up first but this is easily done. Authors include Brian McLaren & Leonard Sweet. Alleon's focus is on 'missional communities' and the site has discussion groups and a leadership network.
Communicating Christ on the Internet by Dr Arne Fjelstad offers articles, links, and a summary of his PhD research on cyberchurch.